Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $119.46   5.251%   $125.7328   $125.73   $125.75   $125.70  
  Purchase #2 $62.76   7.535%   $67.489   $67.49   $67.50   $67.50  
  Purchase #3 $18.74   13.202%   $21.2141   $21.21   $21.20   $21.20  
  Purchase #4 $97.91   4.367%   $102.1857   $102.19   $102.20   $102.20  
  Purchase #5 $82.64   8.463%   $89.6338   $89.63   $89.65   $89.60  
  Purchase #6 $92.99   5.391%   $98.0031   $98.00   $98.00   $98.00  
  Purchase #7 $19.70   8.719%   $21.4176   $21.42   $21.40   $21.40  
  7 purchase totals = $494.20       $525.6761   $525.67   $525.70   $525.60